The Dual Role of the Neonatal Fc Receptor (FcRn) in Podocytes

新生儿 Fc 受体 (FcRn) 在足细胞中的双重作用

基本信息

批准号：
9117538
负责人：
JUDITH T., BLAINE
金额：
$ 31.1万
依托单位：
UNIVERSITY OF COLORADO DENVER
依托单位国家：
美国
项目类别：
财政年份：
2015
资助国家：
美国
起止时间：
2015-09-01 至 2020-07-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9117538
关键词：
Active Biological Transport Albumins Animals Antibodies Antigen Presentation Antigen-Antibody Complex Antigens Area Attenuated Blood Volume CD4 Positive T Lymphocytes Cell Communication Cells Complex Coupled Data Dendritic Cells Development Disease Disease Progression Endothelial Cells Exposure to Filtration Glomerular basement membrane antibody Glomerulonephritis Health Human Imaging Techniques Immune Immunoglobulin G Kidney Kidney Diseases Kidney Failure Knock-out Knockout Mice Knowledge Lead Lysosomes MHC Class II Genes Mediating Microscopy Modeling Molecular Nephritis Nephrotic Syndrome Pathway interactions Process Proteins Proteinuria Proteolytic Processing Renal glomerular disease Role Serum Proteins Severities Severity of illness T-Cell Activation T-Lymphocyte Time Tubular formation Up-Regulation Work base cell type clinically relevant design effective therapy glomerular basement membrane glomerular filtration glomerulosclerosis in vivo in vivo Model intravital microscopy macromolecule mouse model neonatal Fc receptor podocyte prevent protein transport slit diaphragm targeted treatment trafficking transcytosis uptake

项目摘要

DESCRIPTION (provided by applicant): In the normal kidney, an enormous volume of blood (180 L) is filtered each day through the glomerular filtration barrier. By even the most conservative estimates, between 1 - 3 g of albumin a day make it through the filtration barrier. Podocytes are a key part of the GFB and the molecular basis of protein trafficking in podocytes is unknown. In preliminary studies, we have found that podocytes actively transcytose two major serum proteins, albumin and immunoglobulin G (IgG), and that transcytosis is the major pathway for handling these proteins. We have also found that trafficking of IgG is more complicated than that of albumin and that podocytes direct trafficking of IgG differently depending on whether IgG is coupled to antigen. In other cell types such as renal tubular cells and endothelial cells, the neonatal Fc receptor (FcRn) is required for transcytosis of albumin and IgG. In dendritic cells, FcRn is required for antigen/IgG (immune complex) trafficking to the lysosome for antigen presentation on MHC Class II. Based on our preliminary studies and the known role of FcRn in other cell types we propose a dual role for FcRn in podocytes. Specifically, we hypothesize that (1) FcRn is required for transcytosis of albumin and IgG through the podocyte and (2) FcRn is required for immune complex presentation in podocytes by directing antigen/IgG complexes to the lysosome for processing and presentation in podocyte MHC II. In this proposal, we will use primary podocytes isolated from wild type and FcRn knockout mice to determine whether FcRn is required for transcytosis of albumin and IgG. We will also determine whether the glomerular sieving coefficient for albumin and IgG is significantly less in wild type versus FcRn knockout mice and whether podocyte-specific knockout of FcRn in vivo leads to protein accumulation within the glomerulus and glomerulosclerosis. We will examine whether FcRn is required to direct antigen/IgG complexes to the lysosome for degradation and antigen presentation on podocyte MHC Class II and determine whether lack of FcRn abrogates antigen/IgG presentation in podocytes. Finally, we will determine whether podocyte-specific knockout of FcRn ameliorates disease in a mouse model of immune-mediated nephritis. We will also use intravital multiphoton microscopy, a dynamic advanced imaging technique, to examine whether podocyte-specific knockout of FcRn reduces T retention times within the glomerulus after induction of immune-mediated nephritis. The work outlined in this proposal is significant because it is the initial step in understanding exactly how serum proteins are trafficked through the podocyte. Protein accumulation in podocytes has been shown to be toxic to podocytes and correlates with podocyte loss and glomerulosclerosis. Knowledge at the molecular level of how proteins are handled by the podocyte will form the basis for the design of rational therapies to prevent protein accumulation in podocytes. An understanding of the dual role of FcRn in podocytes (both in transcytosis and antigen presentation) is also critical to the design of safe and effective therapies to treat immune-mediated glomerular diseases.

描述（由申请人提供）：在正常肾脏中，每天有大量的血液（180 L）通过肾小球滤过屏障进行过滤，即使是最保守的估计，每天也有 1 - 3 g 白蛋白通过。足细胞是 GFB 的关键部分，足细胞中蛋白质运输的分子基础尚不清楚，在初步研究中，我们发现足细胞主动转胞吞两种主要功能。血清蛋白、白蛋白和免疫球蛋白 G (IgG)，转胞吞作用是处理这些蛋白质的主要途径。我们还发现 IgG 的运输比白蛋白的运输更复杂，并且足细胞根据 IgG 是否存在而以不同的方式指导 IgG 运输。在其他细胞类型（如肾小管细胞和内皮细胞）中，新生 Fc 受体 (FcRn) 是白蛋白和 IgG 转胞吞作用所必需的。 FcRn 是抗原/IgG（免疫复合物）运输到溶酶体以在 MHC II 类上呈递抗原所必需的。根据我们的初步研究和 FcRn 在其他细胞类型中的已知作用，我们提出 FcRn 在足细胞中的双重作用。我们发现 (1) FcRn 是白蛋白和 IgG 通过足细胞转胞吞所必需的，(2) FcRn 是通过引导抗原/IgG 在足细胞中呈递免疫复合物所必需的在本提案中，我们将使用从野生型和 FcRn 敲除小鼠中分离的原代足细胞来确定白蛋白和 IgG 的转胞吞是否需要 FcRn。与 FcRn 敲除小鼠相比，野生型小鼠中白蛋白和 IgG 的筛分系数明显较低，以及足细胞特异性敲除体内 FcRn 是否会导致蛋白质积累我们将检查是否需要 FcRn 将抗原/IgG 复合物引导至溶酶体，以在足细胞 MHC II 上进行降解和抗原呈递，并确定缺乏 FcRn 是否会消除足细胞中的抗原/IgG 呈递。确定足细胞特异性敲除 FcRn 是否可以改善免疫介导性肾炎小鼠模型中的疾病。活体多光子显微镜是一种动态先进成像技术，用于检查足细胞特异性敲除 FcRn 是否会减少免疫介导性肾炎诱导后肾小球内 T 的保留时间。该提案中概述的工作意义重大，因为它是理解的第一步。足细胞中的蛋白质积累已被证明对足细胞有毒，并与足细胞损失和肾小球硬化症相关。足细胞如何处理蛋白质的分子水平知识将成为设计合理疗法以防止足细胞中蛋白质积累的基础。了解 FcRn 在足细胞中的双重作用（转胞吞作用和抗原呈递）也将成为设计的基础。对于设计治疗免疫介导的肾小球疾病的安全有效的疗法至关重要。